Minor Faults in the San Andreas System

Frankel and others [1996] judged that faults with slip rates <0.1 mm/yr and lengths <15 km contribute negligibly to seismic hazard and that regional background seismicity rates reasonably accounted for hazards from such minor faults. Thus for the San Andreas system exclusive of the Great Valley thrusts, only ten low slip rate (²2 mm/yr) faults remain in the final database as L01 through L10 and are listed in Table A-1 in order of decreasing moment rate. Indeed, even many of these remaining faults probably have negligible impact on the regional seismic hazard, especially those that lie close to the major faults. The longest faults, such as Rinconada and Greenville, may well rupture in smaller segments, but in our final data table we indicate only a maximum rupture length, a maximum magnitude, and a proportionately long recurrence time. For all of these minor faults with maximum M_w>6.5 , the methodology of Frankel and others [1996] and Petersen and others [1996a, b] distributes half of the seismic moment rate into a Gutenberg-Richter function with a M_w 6.5 lower bound. Thus, an approximate likelihood of shorter segments and recurrence times is contained in the hazard analysis.